Surgical wires are used in a variety of surgical procedures, such as, for example, reconstructive spine surgeries (such as fusions), spine trauma surgery, total hip arthroplasty, open heart surgery, closures of the sternum, oral/facial surgery to fix mandibular fractures and the like, repair of trochanteric osteotomies and fracture fixation including long bone fractures, adjunct fixation of plates to bone, repair of olecronon fractures, repair of patella fractures and the repair, reconstruction or augmentation of soft tissues such as sprained or ruptured ligaments and tendons.
In surgical and orthopedic operative techniques, it is frequently necessary to fix bone parts, which have been separated surgically or because of fracture, in an exact mutual position and to join them together under pressure. For such osteosynthesis, a monofilament wire is used to encircle broken bones to hold them together. Multi-filament cables also are known for such uses. These wires or cables must either be crimped or twisted together to secure them with a desired tension and a desired location.
The amount of force which is applied to the bone is very important. If too great a tractive force is applied by the cable or wire, a vascular necrosis could be created in the bone around which the cable or wire is wrapped. However, if the tractive force is too low in magnitude, the bone parts are not properly held in the desired position for proper mechanical fixation thereof. Also, if a wire is used and it is twisted too tightly, a fracture of the wire could occur. Thus, a great deal of skill is required to provide the proper tractive force or tension on the wire or cable at the time of installation, even if the surgeon uses the many tools which are commercially available.
Often, the wire or cable must be used in a subcutaneous area. Therefore, it is desirable to render the bulk of the wire or cable as well as the joint where the wire or cable is affixed to itself as compact as possible to minimize discomfort to the patient and damage to the surrounding tissue.
Crimping is typically preferred to twisting of a wire or cable. Twisting of a wire tends to produce a bulky joint, and can cause the wire to break, requiring replacement of the wire. Also, twisting of the wire leaves exposed sharp ends which can cause irritation and damage to the surrounding tissue. Moreover, experimental data demonstrates that crimped wire is stronger than wire that has been twisted or tied. Finally, if the ends of a wire are twisted together, the resulting tractive force of the wire can only be determined by feel and therefore, often, force is very inaccurately applied to the bone.
Even crimping has its drawbacks, primarily because existing tools are not convenient to use. More than one tool often is required to tighten and then crimp a wire. A first tool must tighten the wire to its desired tractive force, and a second tool is required to crimp the wire to hold it in position. As a result, with such systems, a single person has difficulty in doing all that needs to be done with the required degree of accuracy and care.
None of the available prior art systems adequately solves all of the foregoing problems. In particular, a system manufactured by Codman & Shurtleff, Inc. requires the use of a torque driver for tightening the cable, and a separate set of pliers for cinching the cable. Another system developed by John M. Cuckler at the University of Pennsylvania requires a self-locking tensioner which maintains the desired tension, and a second crimper for securing the wire in place. The Dall-Miles trochanter cable grip system offered by Howmedica requires separate cable tensioning and crimping devices. All of these systems necessitate considerable dexterity on the part of the surgeon, and can be difficult to use in circumstances in which the surgical site is difficult to reach or in which the bone has been fractured in a number of places.
Apparatus has been designed to both tension and crimp the wire. However, such devices have not achieved broad commercial success, because they are often difficult to use. In particular, in U.S. Pat. No. 5,116,340, operation of the tightening device requires a torque wrench which requires two hands and can be awkward to use. The apparatus shown in U.S. Pat. No. 4,587,963, provides a separate arm for tightening which is spaced from the handles of the instrument. The position of this arm renders the apparatus difficult to use with one hand.
It is therefore an object of the present invention to provide a single tool which both tightens and crimps a surgical wire.
It is another object of the present invention to provide a tool which both tightens and crimps a surgical wire and which can be readily used by the surgeon, with one hand.
It is a further object of the present invention to provide a tool and method which produces a high strength, low bulk crimp suitable for a subcutaneous location.